Defence Watch is reporting that coalition air strikes have killed 20 000 ISIS members, which means an unknown but likely high number of wounded. I don't think IS battlefield medicine is of a NATO standard, meaning that many of the killed would likely have survived in other circumstances. Still, 20 000 is a lot. To put in perspective, it's nearly half of the more than 50 000 US troops killed in the Vietnam/American War.
Yet IS remains, far less resourced than the Russians, US, and their allies. Still it is able to hold ground and sustain itself while the bombs fall, and the Russians and Americans squabble over strategy and air space and menace each other.
I suppose it's possible that the mix of efforts targeting IS (and related groups), however organisationally dysfunctional, will break its back in terms of its logistics and personnel, but I'm not sure that leaves anyone particularly better off. Afghanistan and Bushed Iraq both show that motivated armed groups are able to dissolve and wage a very persistent guerrilla war against any occupying force and any returning residents. The region will be very unsafe for the foreseeable future, perhaps indefinitely, regardless of whether IS remains intact and able to hold territory. The Assad regime or whatever replaces it will be busy for years to come, at least until climate driven drought destroys the water supply and food security of the region and the regime collapses into more violence. Displaced militants, especially those with foreign passports will flee and head to Saudi Arabia, Europe and elsewhere, creating more headaches for the security services in those places. Gulf states especially may be prone severe upset due to the large numbers of IS sympathisers in those places.
Any force that can sustain 20K dead and still hold ground isn't going to fold easily under more bombs. Maybe a solution rests less in dropping bombs, than in drying up the supply of food, fuel, arms and money that sustain IS and its mimics - basically ring-fencing Syria and Iraq, and making possible - where possible - the safe exit and relocation of refugees. Nope, instead the US, Russia, Iran, et al will continue to shovel arms into the place and Europe will continue to shit itself over consequent refugee flows. If it continues long enough, Israel will get seriously involved and things will get even weirder.
In the post-9/11 era, none try to end wars. The powers that be used to do that, often through ham-fisted, bungling attempts, but the shooting stopped in the Balkans, Cyprus, Vietnam, and a host of other places. Now instead they institutionalise multi-year bombing campaigns and low-intensity land-wars, which are just continuations of existing wars. War can now be waged below the public casuality tolerance threshold, making it easier to use military force as a normative policy tool against enemies that pose minimal material threat to Western forces.
I can tell you that if Russia or the US and its allies lost 20 000 troops to IS, they'd be using mach numbers to measure the pace of withdrawal. It continues because it's easy.